Surgery of the heart is a common surgical procedure and about 600,000 are currently performed in the worldwide each year, of which about half take place in the U.S. Most heart operations involve coronary artery bypass grafting, but a significant number involve heart valve replacement or repair, including replacement or valvuloplasty of mitral and tricuspid valves. This surgical technique requires adequate exposure of the valve annulus. Good exposure of the mitral valve is a difficult problem in some patients due to individual anatomy. The heart is usually exposed by a sternal midline incision. Following the opening of the sternum a sternal retractor is used to open the sternum a distance of several inches.
In general, the typical retractor consists of two sternal blades attached, respectively, to a pair of arms. One arm is rigidly attached to a rack containing a single row of gear teeth, and the second arm rigidly fixed to a moving member that is able to slide along the rack. A rotatable handle, hinged to a simple cog gear is contained in the moving member and engages the rack. Rotation of the handle caused the member to move along the rack, thus changing the separation distance between the sternal blades.
While surgical retractors, in general, perform the same function--spreading apart two adjacent anatomical structures to permit access by the surgeon--the requirements for a satisfactory retractor for one purpose differ greatly from requirements for a retractor intended for a different surgical procedure. Thus, there is no basis for extrapolating a function, structure or concept from one kind of retractor to another kind of retractor. A rib cage retractor, or a back retractor, for example, teaches little of any value or relevance with respect to a sternal retractor or a jaw retractor.
An example of a sternal retractor of the general type of which the present invention is an improvement is described in U.S. Pat. No. 5,772,583, Wright, et. al., The Wright, et. al., patent also describes and refers to several other retractors that constitute prior art as to the present invention.
It is important in some surgical procedures to be able to position the retractor operating mechanism without retractor blades attached and/or to be able to use any of a plurality of blades of different sizes and shapes--being able to interchange blades as need during surgery. This result has not been reasonably possible using prior art retractors. Indeed, the general approach has been to select a given retractor and then to modify surgical procedures as necessary to accommodate the selected retractor.